Due to advances in communication systems, various wireless terminals have introduced to customers such as companies and individuals. Mobile communication systems have employed technologies related to 3rd generation partnership project (3GPP)-series Long Term Evolution (LTE) and LTE-Advanced systems. Such mobile communication systems are capable of transmitting a large amount of data at a high speed. In order for transmitting a large amount of data at a high speed, data may be efficiently transmitted using several cells.
However, there is a limit in transmitting a large amount of data to several terminals from a base station using limited frequency resources. For example, specific service providers have occupied predetermined frequency resources exclusively. Accordingly, it is difficult and very expensive to secure frequency resources.
Unlike licensed spectrum that is exclusively occupied by a specific service provider, unlicensed spectrum band can be shared. For example, Wireless Local Area Network (WLAN) technology is representative of WiFi, and such WLAN provides a data transmission/reception service using a frequency resource of unlicensed spectrum bands.
Accordingly, there is a need for a method for enabling a mobile communication system to transmit/receive data to/from a terminal using WLAN Access Point (AP). In particular, no detailed procedure and method have introduced for enabling the base station to transmit data to and receive data from a terminal using a WLAN radio resource (e.g., WLAN carrier) and a base station radio resource (e.g., base station carrier). Accordingly, there is a need for a detailed method of setting a detailed uplink data transmission path and setting and transmitting buffer setting information of a terminal for a radio bearer, in which a terminal is set to transmit uplink data, using a WLAN radio resource and a base station radio resource.